Clinical, morphologic, and genomic findings in ROS1 fusion Spitz neoplasms

Exploring the therapeutic potential of rabdoternin E in lung cancer treatment: Targeting the ROS/p38 MAPK/JNK signaling pathway

Lung cancer has the highest incidence and mortality rates of all cancer types in China and therefore represents a serious threat to human health. In the present study, the mechanism of rabdoternin E against the proliferation of the lung cancer cell line A549 was explored. It was found that rabdoternin E caused the accumulation of large amounts of reactive oxygen species (ROS), promoted cell S phase arrest by reducing the expression of CDK2 and cyclin A2, induced apoptosis by increasing the Bax/Bcl‑2 ratio and promoted the phosphorylation of proteins in the ROS/p38 MAPK/JNK signaling pathway, which is associated with apoptosis and ferroptosis. In addition, it was also found that Z‑VAD‑FMK (an apoptosis inhibitor), ferrostatin‑1 (ferroptosis inhibitor) and N‑acetylcysteine (a ROS inhibitor) could partially or greatly reverse the cytotoxicity of rabdoternin E to A549 cells. Similarly, NAC (N‑acetylcysteine) treatment notably inhibited the rabdoternin E‑stimulated p38 MAPK and JNK activation. Furthermore, in vivo experiments in mice revealed that Rabdoternin E markedly reduced tumor volume and weight and regulated the expression levels of apoptosis and ferroptosis‑related proteins (including Ki67, Bcl‑2, Bax, glutathione peroxidase 4, solute carrier family 7 member 11 and transferrin) in the tumor tissues of mice. Histopathological observation confirmed that the number of tumor cells decreased markedly after administration of rabdoternin E. Taken together, rabdoternin E induced apoptosis and ferroptosis of A549 cells by activating the ROS/p38 MAPK/JNK signaling pathway. Therefore, the results of the present study showed that rabdoternin E is not toxic to MCF‑7 cells (normal lung cells), had no significant effect on body weight and was effective and therefore may be a novel therapeutic treatment for lung cancer.

Heterogeneous pathogenesis of melanoma: BRAF mutations and beyond

Melanoma pathogenesis, conventionally perceived as a linear accumulation of molecular changes, discloses substantial heterogeneity driven by non-linear biological processes, including the direct transformation of melanocyte stem cells. This heterogeneity manifests in diverse biological phenotypes and developmental states, influencing variable responses to treatments. Unveiling the aberrant mechanisms steering melanoma initiation, progression, and metastasis is imperative. Beyond mutations in oncogenic and tumor suppressor genes, the involvement of distinct molecular pathways assumes a pivotal role in melanoma pathogenesis. Ultraviolet (UV) radiations, a principal factor in melanoma etiology, categorizes melanomas based on cumulative sun damage (CSD). The genomic landscape of lesions correlates with UV exposure, impacting mutational load and spectrum of mutations. The World Health Organization's 2018 classification underscores the interplay between sun exposure and genomic characteristics, distinguishing melanomas associated with CSD from those unrelated to CSD. The classification elucidates molecular features such as tumor mutational burden and copy number alterations associated with different melanoma subtypes. The significance of the mutated BRAF gene and its pathway, notably BRAFV600 variants, in melanoma is paramount. BRAF mutations, prevalent across diverse cancer types, present therapeutic avenues, with clinical trials validating the efficacy of targeted therapies and immunotherapy. Additional driver mutations in oncogenes further characterize specific melanoma pathways, impacting tumor behavior. While histopathological examination remains pivotal, challenges persist in molecularly classifying melanocytic tumors. In this review, we went through all molecular characterization that aid in discriminating common and ambiguous lesions. Integration of highly sensitive molecular diagnostic tests into the diagnostic workflow becomes indispensable, particularly in instances where histology alone fails to achieve a conclusive diagnosis. A diagnostic algorithm based on different molecular features inferred by the various studies is here proposed.

Mechanisms of tropomyosin 3 in the development of malignant tumors

Tropomyosin (TPM) is an important regulatory protein that binds to actin in fine myofilaments, playing a crucial role in the regulation of muscle contraction. TPM3, as one of four tropomyosin genes, is notably prevalent in eukaryotic cells. Traditionally, abnormal gene expression of TPM3 has been exclusively associated with myopathy. However, recent years have witnessed a surge in studies highlighting the close correlation between abnormal expression of TPM3 and the onset, progression, metastasis, and prognosis of various malignant tumors. In light of this, investigating the mechanisms underlying the pathogenetic role of TPM3 holds significant promise for early diagnosis and more effective treatment strategies. This article aims to provide an insightful review of the structural characteristics of TPM3 and its intricate role in the occurrence and development of malignant tumors.

Comparative Performance Analysis of Idylla and Archer in the Detection of Gene Fusions in Spitzoid Melanocytic Tumors

Melanocytic neoplasms with spitzoid histomorphology are often difficult to classify without identifying genetic drivers such as kinase fusions. Traditional diagnostic methods, such as immunohistochemistry, can yield inconclusive results, and advanced techniques such as the Archer fusion assay are often inaccessible and costly. The Idylla GeneFusion Assay might offer a rapid and cost-effective alternative. This study compared Idylla and Archer in identifying ALK, pan-NTRK, RET, and ROS1 gene fusions. Of the 147 samples where next-generation sequencing did not detect genetic drivers, 89 (60.5%) meeting the tissue requirements were further analyzed using Idylla (Cohort A). Idylla demonstrated a sensitivity of 75% and a specificity of 100% in detecting these fusions. Additionally, among 27 randomly selected cases (Cohort B) that failed to meet the inclusion criteria, Idylla maintained the same levels of sensitivity and specificity. Our findings also show that Idylla can be effectively conducted with isolated RNA, broadening its applicability beyond tissue samples. Although the Idylla assay may not replace more comprehensive molecular assays such as Archer, it could serve as a valuable initial screening tool in diagnosing spitzoid melanocytic tumors.

Novel gene fusion discovery in Spitz tumours and its relevance in diagnostics

In addition to morphologic analysis, molecular diagnostic work up of Spitz tumours is often of great value for their accurate diagnosis/classification. Nowadays, next-generation sequencing (NGS) is the predominant screening method in molecular diagnostics. Up to 80% of these melanocytic neoplasms comprise gene fusions as genetic anomalies for which the driver codes for a protein harbouring a kinase domain. However, because of the variety of fusion partners the use of PCR-based targeted enrichment NGS methods is not recommended. We describe a series of four Spitz tumour samples in which distinct gene fusions were detected by hybridisation-based capture NGS (TPM3::ALK, LIMA1::ROS1, LRRFIP2::ROS1 and MYO5A::RET). Two of these fusions are not previously described. All 4 fusions were confirmed by reverse transcription-PCR. These findings demonstrate the need for molecular analysis that can detect unknown fusions in Spitz neoplasms for optimal diagnosis.

Current treatment and novel insights regarding ROS1-targeted therapy in malignant tumors

BACKGROUND

The proto-oncogene ROS1 encodes an intrinsic type I membrane protein of the tyrosine kinase/insulin receptor family. ROS1 facilitates the progression of various malignancies via self-mutations or rearrangements. Studies on ROS1-directed tyrosine kinase inhibitors have been conducted, and some have been approved by the FDA for clinical use. However, the adverse effects and mechanisms of resistance associated with ROS1 inhibitors remain unknown. In addition, next-generation ROS1 inhibitors, which have the advantage of treating central nervous system metastases and alleviating endogenous drug resistance, are still in the clinical trial stage.

METHOD

In this study, we searched relevant articles reporting the mechanism and clinical application of ROS1 in recent years; systematically reviewed the biological mechanisms, diagnostic methods, and research progress on ROS1 inhibitors; and provided perspectives for the future of ROS1-targeted therapy.

RESULTS

ROS1 is most expressed in malignant tumours. Only a few ROS1 kinase inhibitors are currently approved for use in NSCLC, the efficacy of other TKIs for NSCLC and other malignancies has not been ascertained. There is no effective standard treatment for adverse events or resistance to ROS1-targeted therapy. Next-generation TKIs appear capable of overcoming resistance and delaying central nervous system metastasis, but with a greater incidence of adverse effects.

CONCLUSIONS

Further research on next-generation TKIs regarding the localization of ROS1 and its fusion partners, binding sites for targeted drugs, and coadministration with other drugs is required. The correlation between TKIs and chemotherapy or immunotherapy in clinical practice requires further study.

Kinase Fusions in Spitz Melanocytic Tumors: The Past, the Present, and the Future

In recent years, particular interest has developed in molecular biology applied to the field of dermatopathology, with a focus on nevi of the Spitz spectrum. From 2014 onwards, an increasing number of papers have been published to classify, stratify, and correctly frame molecular alterations, including kinase fusions. In this paper, we try to synthesize the knowledge gained in this area so far. In December 2023, we searched Medline and Scopus for case reports and case series, narrative and systematic reviews, meta-analyses, observational studies-either longitudinal or historical, case series, and case reports published in English in the last 15 years using the keywords spitzoid neoplasms, kinase fusions, ALK, ROS1, NTRK (1-2-3), MET, RET, MAP3K8, and RAF1. ALK-rearranged Spitz tumors and ROS-1-rearranged tumors are among the most studied and characterized entities in the literature, in an attempt (although not always successful) to correlate histopathological features with the probable molecular driver alteration. NTRK-, RET-, and MET-rearranged Spitz tumors present another studied and characterized entity, with several rearrangements described but as of yet incomplete information about their prognostic significance. Furthermore, although rarer, rearrangements of serine-threonine kinases such as BRAF, RAF1, and MAP3K8 have also been described, but more cases with more detailed information about possible histopathological alterations, mechanisms of etiopathogenesis, and also prognosis are needed. The knowledge of molecular drivers is of great interest in the field of melanocytic diagnostics, and it is important to consider that in addition to immunohistochemistry, molecular techniques such as FISH, PCR, and/or NGS are essential to confirm and classify the different patterns of mutation. Future studies with large case series and molecular sequencing techniques are needed to allow for a more complete and comprehensive understanding of the role of fusion kinases in the spitzoid tumor family.

[Clinical, histological and genetic correlations in melanocytic tumours with chromosomal rearrangements]

In some tumoral subtypes chromosomal translocations lead to an oncogenic chimeric protein acting as a tumorigenesis driver event. The main fusion model combines the promoter swapping of an inactivated tumor suppressor gene and a functional kinase that evades its regulatory system. The range of described fusions keeps growing in the 2023 WHO classification of melanocytic tumours. It is not limited to the group of Spitz tumours as previously but now extends to blue tumours and dermal tumours with a melanocytic phenotype. Molecular pathology helps detect these anomalies using clinical and morphological features. This analysis is essential as this strongly conditions the adapted local treatment of such tumours who are often overtreated.

Spitz Tumors and Melanoma in the Genomic Age: A Retrospective Look at Ackerman's Conundrum

After 25 years, "Ackerman's conundrum", namely, the distinction of benign from malignant Spitz neoplasms, remains challenging. Genomic studies have shown that most Spitz tumors harbor tyrosine and serine/threonine kinase fusions, including ALK, ROS1, NTRK1, NTRK2, NTRK3, BRAF and MAP3K8, or some mutations, such as HRAS and MAP3K8. These chromosomal abnormalities act as drivers, initiating the oncogenetic process and conferring basic bio-morphological features. Most Spitz tumors show no additional genomic alterations or few ones; others harbor a variable number of mutations, capable of conferring characteristics related to clinical behavior, including CDKN2A deletion and TERT-p mutation. Since the accumulation of mutations is gradual and progressive, tumors appear to form a bio-morphologic spectrum, in which they show a progressive increase of clinical risk and histological atypia. In this context, a binary classification Spitz nevus-melanoma appears as no longer adequate, not corresponding to the real genomic substrate of lesions. A ternary classification Spitz nevus-Spitz melanocytoma-Spitz melanoma is more adherent to the real neoplastic pathway, but some cases with intermediate ambiguous features remain difficult to diagnose. A prognostic stratification of Spitz tumors, based on the morphologic and genomic characteristics, as a complement to the diagnosis, may contribute to better treatment plans for patients.

A reappraisal of the epidemiology of Spitz neoplasms in the molecular era: A retrospective cohort study

BACKGROUND

Previous studies suggest that Spitz neoplasms occur primarily in younger patients, leading pathologists to shy away from diagnosing a benign Spitz neoplasm in the elderly. With the advent of genomic sequencing, there is a need for reappraisal of the epidemiology of Spitz neoplasms in the modern molecular era.

OBJECTIVE

We aim to reassess the epidemiology of Spitz neoplasms incorporating next-generation sequencing.

METHODS

We looked at 53,814 non-Spitz neoplasms and 1260 Spitz neoplasms including 286 Spitz neoplasms with next-generation sequencing testing and collected various epidemiologic data.

RESULTS

In our general pool of cases, the proportion of Spitz neoplasm cases occurring is relatively the same in each of the first 4 decades of life with a precipitous drop in the fifth decade. In assessing a group of genomically verified cases of Spitz neoplasms, the drop was much less significant and up to 20% of all Spitz neoplasm cases occurred in patients over 50 years of age.

LIMITATIONS

Limitations included the number of genetically verified Spitz neoplasm cases available and a possible bias as to which cases undergo genomic testing.

CONCLUSION

Genomic verification may allow more confident diagnosis of Spitz neoplasms in patients over 50 years of age and avoid melanoma overdiagnosis.

Cutaneous melanoma

Cutaneous melanoma is a malignancy arising from melanocytes of the skin. Incidence rates are rising, particularly in White populations. Cutaneous melanoma is typically driven by exposure to ultraviolet radiation from natural sunlight and indoor tanning, although there are several subtypes that are not related to ultraviolet radiation exposure. Primary melanomas are often darkly pigmented, but can be amelanotic, with diagnosis based on a combination of clinical and histopathological findings. Primary melanoma is treated with wide excision, with margins determined by tumour thickness. Further treatment depends on the disease stage (following histopathological examination and, where appropriate, sentinel lymph node biopsy) and can include surgery, checkpoint immunotherapy, targeted therapy, or radiotherapy. Systemic drug therapies are recommended as an adjunct to surgery in patients with resectable locoregional metastases and are the mainstay of treatment in advanced melanoma. Management of advanced melanoma is complex, particularly in those with cerebral metastasis. Multidisciplinary care is essential. Systemic drug therapies, particularly immune checkpoint inhibitors, have substantially increased melanoma survival following a series of landmark approvals from 2011 onward.

Spectrum of Melanocytic Tumors Harboring BRAF Gene Fusions: 58 Cases With Histomorphologic and Genetic Correlations

We report a series of 58 melanocytic tumors that harbor an activating fusion of BRAF, a component of the mitogen-activated protein kinase (MAPK) signaling cascade. Cases were diagnosed as melanocytic nevus (n = 12, 21%), diagnostically ambiguous favor benign (n = 22, 38%), and diagnostically ambiguous concerning for melanoma (n = 12, 21%) or melanoma (n = 12, 21%). Three main histopathologic patterns were observed. The first pattern (buckshot fibrosis) was characterized by large, epithelioid melanocytes arrayed as single cells or "buckshot" within marked stromal desmoplasia. The second pattern (cords in whorled fibrosis) demonstrated polypoid growth with a whorled arrangement of cords and single melanocytes within desmoplasia. The third pattern (spindle-cell fascicles) showed fascicular growth of spindled melanocytes. Cytomorphologic features characteristic of Spitz nevi were observed in most cases (n = 50, 86%). Most of the cases (n = 54, or 93%) showed stromal desmoplasia. Histomorphology alone was not sufficient in distinguishing benign from malignant melanocytic tumors with BRAF fusion gene because the only histopathologic features more commonly associated with a diagnosis of malignancy included dermal mitoses (P = .046) and transepidermal elimination of melanocytes (P = .013). BRAF fusion kinases are targetable by kinase inhibitors and, thus, should be considered as relevant genetic alterations in the molecular workup of melanomas. Recognizing the 3 main histopathologic patterns of melanocytic tumors with BRAF fusion gene will aid in directing ancillary testing.

An update on genomic aberrations in Spitz naevi and tumours

Spitz neoplasms continue to be a diagnostic challenge for dermatopathologists and are defined by distinctive morphological and genetic features. With the recent advancements in genomic sequencing, the classification, diagnosis, and prognostication of these tumours have greatly improved. Several subtypes of Spitz neoplasms have been identified based on their specific genomic aberrations, which often correlate with distinctive morphologies and biological behaviour. These genetic driver events can be classified into four major groups, including: (1) mutations [HRAS mutations (with or without 11p amplification) and 6q23 deletions]; (2) tyrosine kinase fusions (ROS1, ALK, NTRK1-3, MET and RET); (3) serine/threonine kinase fusions and mutations (BRAF, MAP3K8, and MAP2K1); and (4) other rare genomic aberrations. These driver genomic events are hypothesised to enable the initial proliferation of melanocytes and are often accompanied by additional genomic aberrations that affect biological behaviour. The discovery of theses genomic fusions has allowed for a more objective definition of a Spitz neoplasm. Further studies have shown that the majority of morphologically Spitzoid appearing melanocytic neoplasms with aggressive behaviour are in fact BRAF or NRAS mutated tumours mimicking Spitz. Truly malignant fusion driven Spitz neoplasms may occur but are relatively uncommon, and biomarkers such as homozygous 9p21 (CDKN2A) deletions or TERT-p mutations can have some prognostic value in such cases. In this review, we discuss the importance and various methods of identifying Spitz associated genomic fusions to help provide more definitive classification. We also discuss characteristic features of the various fusion subtypes as well as prognostic biomarkers.

Case report: complete remission with crizotinib in ROS1 fusion-positive sinonasal mucosal melanoma

Introduction

Sinonasal mucosal melanoma (SNMM) originates from melanocytes. Currently, the main treatment methods, including surgery, radiotherapy and chemotherapy, have little effect on the recurrence and metastasis of SNMM. However, targeted therapy may be a breakthrough in treating SNMM.

Methods

A SNMM patient with ROS1 fusion received 250mg Crizotinib capsule (2 times a day, 1 tablet each time) therapy.

Results

The patient achieved partial remission after 4 months of treatment and complete remission after 8 months of treatment.

Conclusion

Our findings suggest that crizotinib can be an option to improve overall survival and quality of life of patients with metastatic ROS1-fusion SNMM. We believe that our report will provide insights for the application of crizotini in the treatment of melanoma.

PRAME Expression Correlates With Genomic Aberration and Malignant Diagnosis of Spitzoid Melanocytic Neoplasms

ABSTRACT

Spitzoid melanocytic neoplasms are a diagnostically challenging class of lesions in dermatopathology. Recently, molecular assays and immunohistochemical markers have been explored as ancillary methods to assist in the diagnostic workup. Specifically, preferentially expressed antigen in melanoma (PRAME) immunohistochemistry is a nuclear stain commonly positive in melanomas, but not in nevi. This study investigates PRAME immunoreactivity (≥75% positive nuclear staining in tumor cells) in a set of 59 spitzoid melanocytic neoplasms with known clinical outcomes. We compared PRAME status with (1) the clinical outcomes, (2) the morphologic diagnoses, and (3) the status of TERT promoter mutation. Regarding clinical outcomes, 3 cases developed metastatic disease, of which 2 expressed diffusely positive PRAME staining. Of the 56 cases that did not show evidence of metastasis, 6 expressed diffusely positive PRAME staining. Morphologically, diffusely positive PRAME staining was seen in 7 of 21 cases (33.3%) diagnosed as melanoma and only 1 benign tumor 1 of 38 (2.6%). There were 4 of 8 cases with a TERT promoter mutation which were diffusely PRAME-positive compared with 4 of 51 cases without TERT promoter mutation ( P = 0.001). Our results show a statistically significant correlation between PRAME expression and the diagnosis, outcome, and TERT promoter mutation status of atypical spitzoid melanocytic neoplasms, suggesting immunohistochemistry for PRAME can help support a suspected diagnosis. However, because of occasional false-positive and negative test results, correlation with the clinical and histologic findings as well as results from other tests is needed for the interpretation of diagnostically challenging spitzoid melanocytic neoplasms.

Modeling Spitz melanoma in zebrafish using sequential mutagenesis

Spitz neoplasms are a diverse group of molecularly and histologically defined melanocytic tumors with varying biologic potentials. The precise classification of Spitz neoplasms can be challenging. Recent studies have revealed recurrent fusions involving multiple kinases in a large proportion of Spitz tumors. In this study, we generated a transgenic zebrafish model of Spitz melanoma using a previously identified ZCCHC8-ROS1 fusion gene. Animals developed grossly apparent melanocytic proliferations as early as 3 weeks of age and overt melanoma as early as 5 weeks. By 7 weeks, ZCCHC8-ROS1 induced a histologic spectrum of neoplasms ranging from hyperpigmented patches to melanoma. Given the swift onset of these tumors during development, we extended this approach into adult fish using a recently described electroporation technique. Tissue-specific expression of ZCCHC8-ROS1 in adults led to melanocyte expansion without overt progression to melanoma. Subsequent electroporation with tissue-specific CRISPR, targeting only tp53 was sufficient to induce transformation to melanoma. Our model exhibits the use of sequential mutagenesis in the adult zebrafish, and demonstrates that ZCCHC8-ROS1 induces a spectrum of melanocytic lesions that closely mimics human Spitz neoplasms.

Summary: We describe the first animal model of Spitz neoplasms and demonstrate its use for modeling sequential mutagenesis and its potential for studying melanocyte development in vivo.

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

"Concomitant" Cutaneous and Nodal Spitz Nevus/Tumor: A New Scenario for an Old Problem

ABSTRACT

Spitz tumors are notoriously characterized by a high propensity to nodal involvement with a morphologically malignant (intraparenchymal) pattern but with little or no tendency toward further spread. We describe a case of spindle cell Spitz neoplasm removed from the thigh in a 34-year-old woman and initially diagnosed as "Spitzoid melanoma;" the sentinel node was characterized by a morphologically benign pattern of nodal involvement, with prevailingly capsular and septal aggregated of melanocytes showing the same cytomorphological features as the cutaneous tumor. Both the cutaneous and the nodal tumor were strongly ROS1-positive on immunohistochemistry; rearrangement of the ROS1 gene was confirmed with fluorescence in situ hybridization on the cutaneous tumor. The clonal relationship between the cutaneous and the nodal capsular/trabecular tumor, as established by their morphological and immunophenotypical resemblance, underlines the existence of a morphologically benign pattern of spread of Spitz neoplasms, as also suggested by the occurrence of eruptive Spitz nevi.

RASGRF1-rearranged Cutaneous Melanocytic Neoplasms With Spitzoid Cytomorphology: A Clinicopathologic and Genetic Study of 3 Cases

Spitz neoplasms, according to 2018 WHO Blue Book, are morphologically defined by spindled and/or epithelioid melanocytes and genetically by either HRAS mutations or kinase gene fusions. The terminology "spitzoid" refers to lesions with similar morphology but with alternate or undefined genetic anomalies. Herein, we present 3 melanocytic neoplasms with a spitzoid cytomorphology, variable nuclear atypia, and harboring undescribed fusions involving RASGRF1. Two cases presented as unpigmented papules on the heel of a 26-year-old female (case 1) and the forearm of a 13-year-old boy (case 2). They were classified as low-grade melanocytomas (WHO 2018). The third case appeared as a pigmented ulcer on the sole of a 72-year-old female (case 3) that displayed diagnostic features of an invasive melanoma (Breslow thickness 6 mm, Clark level V). A wide skin reexcision identified an epidermotropic metastasis, and sentinel lymph node biopsy displayed multiple subcapsular metastatic deposits. RNA sequencing revealed CD63::RASGRF1, EHBP1::RASGRF1, and ABCC2::RASGRF1 fusions in cases 1 to 3, respectively. They were confirmed by a RASGRF1 break-apart fluorescence in situ hybridization technique. Translocations of RASGRF1, a gene coding a guanine nucleotide exchange factor but not a kinase, have rarely been reported in tumors. While all these cases showed spitzoid cytomorphology, it is too early to tell if they are true Spitz neoplasms as currently defined.

The Morpho-Molecular Landscape of Spitz Neoplasms

Spitz neoplasms are a heterogeneous group of melanocytic proliferations with a great variability in the histological characteristics and in the biological behavior. Thanks to recent discoveries, the morpho-molecular landscape of Spitz lineage is becoming clearer, with the identification of subtypes with recurrent features thus providing the basis for a more solid and precise tumor classification. Indeed, specific mutually exclusive driver molecular events, namely HRAS or MAP2K1 mutations, copy number gains of 11p, and fusions involving ALK, ROS, NTRK1, NTRK2, NTRK3, MET, RET, MAP3K8, and BRAF genes, correlate with distinctive histological features. The accumulation of further molecular aberrations, instead, promotes the increasing malignant transformation of Spitz neoplasms. Thus, the detection of a driver genetic alteration can be achieved using the appropriate diagnostic tests chosen according to the histological characteristics of the lesion. This allows the recognition of subtypes with aggressive behavior requiring further molecular investigations. This review provides an update on the morpho-molecular correlations in Spitz neoplasms.

Morphologic features in a series of 352 Spitz melanocytic proliferations help predict their oncogenic drivers

Spitz nevi are indolent melanocytic tumors arising preferentially during and after childhood. Over the last decades, recurrent oncogenic drivers, sparsely detected in melanoma, were identified in Spitz melanocytic proliferations. Therefore, the detection of such drivers appears as a relevant diagnostic tool to distinguish both entities. Interestingly, morphologic features might correlate with the oncogenic drivers. Thus, the goal of this study was to assess the performances of previously identified morphological criteria to predict the presence of specific drivers. In total, 352 Spitz melanocytic proliferations either with a genetically identified oncogenic driver or investigated for ALK, ROS1, and NTRK1 overexpression by immunohistochemistry were enrolled in the present study. The microscopic features of the cases were assessed blindly with regards to the molecular status and, performances of previously described morphological criteria to predict the molecular status were assessed applying the likelihood-ratio test (LHR). Overall, an oncogenic driver was identified in 76% of the cases (n = 268/352). No microscopic features allowed the reliable prediction of ROS1- and NTRK1-overexpressing cases. By contrast, a plexiform pattern can contribute to the recognition of ALK-overexpressing cases (LHR(+) = 6.14). Importantly, the pseudo-schwannoma variant was highly suggestive of NTRK3-rearranged cases (LHR(+) = 43). Moreover, atypical/malignant tumor (LHR(+) = 5.18), severe cellular atypia (LHR(+) = 5.07), and p16 loss (LHR(+) = 14) contribute to the recognition of MAP3K8-rearranged cases, while the presence of a sheet-like architecture (LHR(+) = 5.39) and a marked fibrosis of the stroma (LHR(+)=5.06) were predictive of BRAF-fused tumors. To conclude, our study confirms ALK-overexpressing, NTRK3-, MAP3K8-, and BRAF-rearranged cases harbored distinct morphologic features allowing their microscopic recognition.

Genome-wide copy number variations as molecular diagnostic tool for cutaneous intermediate melanocytic lesions: a systematic review and individual patient data meta-analysis

Cutaneous intermediate melanocytic neoplasms with ambiguous histopathological features are diagnostically challenging. Ancillary cytogenetic techniques to detect genome-wide copy number variations (CNVs) might provide a valuable tool to allow accurate classification as benign (nevus) or malignant (melanoma). However, the CNV cut-off value to distinguish intermediate lesions from melanoma is not well defined. We performed a systematic review and individual patient data meta-analysis to evaluate the use of CNVs to classify intermediate melanocytic lesions. A total of 31 studies and 431 individual lesions were included. The CNV number in intermediate lesions (median 1, interquartile range [IQR] 0-2) was significantly higher (p<0.001) compared to that in benign lesions (median 0, IQR 0-1) and lower (p<0.001) compared to that in malignant lesions (median 6, IQR 4-11). The CNV number displayed excellent ability to differentiate between intermediate and malignant lesions (0.90, 95% CI 0.86-0.94, p<0.001). Two CNV cut-off points demonstrated a sensitivity and specificity higher than 80%. A cut-off of ≥3 CNVs corresponded to 85% sensitivity and 84% specificity, and a cut-off of ≥4 CNVs corresponded to 81% sensitivity and 91% specificity, respectively. This individual patient data meta-analysis provides a comprehensive overview of CNVs in cutaneous intermediate melanocytic lesions, based on the largest pooled cohort of ambiguous melanocytic neoplasms to date. Our meta-analysis suggests that a cut-off of ≥3 CNVs might represent the optimal trade-off between sensitivity and specificity in clinical practice to differentiate intermediate lesions from melanoma.

Cutaneous Melanomas Arising during Childhood: An Overview of the Main Entities

Cutaneous melanomas are exceptional in children and represent a variety of clinical situations, each with a different prognosis. In congenital nevi, the risk of transformation is correlated with the size of the nevus. The most frequent type is lateral transformation, extremely rare before puberty, reminiscent of a superficial spreading melanoma (SSM) ex-nevus. Deep nodular transformation is much rarer, can occur before puberty, and must be distinguished from benign proliferative nodules. Superficial spreading melanoma can also arise within small nevi, which were not visible at birth, usually after puberty, and can reveal a cancer predisposition syndrome (CDKN2A or CDK4 germline mutations). Prognosis is correlated with classical histoprognostic features (mainly Breslow thickness). Spitz tumors are frequent in adolescents and encompass benign (Spitz nevus), intermediate (atypical Spitz tumor), and malignant forms (malignant Spitz tumor). The whole spectrum is characterized by specific morphology with spindled and epithelioid cells, genetic features, and an overall favorable outcome even if a regional lymph node is involved. Nevoid melanomas are rare and difficult to diagnose clinically and histologically. They can arise in late adolescence. Their prognosis is currently not very well ascertained. A small group of melanomas remains unclassified after histological and molecular assessment.

ROS-1 Pattern Of Immunostaining In 11 Cases Of Spitzoid Tumours: Comparison With Histopathological, Fish And Ngs Analysis

AIMS

Spitzoid tumours have been shown to harbour exclusive kinase fusions. Few studies have analysed substantial numbers of ROS-1 rearranged lesions, particularly immunohistochemistry has been poorly investigated.

METHODS AND RESULTS

Among a group of 35 spitzoid tumours, of which 34 consecutively diagnosed in a 3-year period, we found 11 cases ROS-1 positive at immunohistochemistry, belonging to 10 patients, 8 females and 2 males, aged 3 to 52 years (median 29); most lesions (8) were localized on the lower extremities. Four patterns of immunostaining were observed: cytoplasmic granular diffuse (6 cases), sparse cytoplasmic granules (3), paranuclear dots (1), and nuclear (1). All cases resulted rearranged at FISH analysis (cut-off >15%). NGS-RNA analysis featured specific fusions of ROS-1 in 4 cases: two with PWWP2A, one with PPFIBP1, and one with ZCCHC8. NGS-DNA analysis demonstrated in 5 cases specific mutations of AKT, EGFR, NRAS, MYC, ALK, and KIT genes. ROS-1 lesions belonged predominantly to the "Atypical Spitz Tumour" group and featured mainly a nested pattern at histology. Interestingly, one patient developed two lesions ROS-1 positive.

CONCLUSIONS

Immunohistochemistry showed a 100% of sensitivity and specificity compared to FISH results, corresponding to ROS-1 rearrangement in 31% of cases studied. These observations shed new light on the value of immunohistochemical evaluation of ROS-1 in spitzoid tumours. ROS-1 patterns of immunostaining probably reflect different subcellular localizations of ROS-1 fusions, although no specific correlations were found in cases studied. Immunohistochemistry and FISH resulted the most sensitive techniques in detecting ROS-1 rearrangement in this subset of neoplasms.